Multiple Outputs

Started by abefanning September 13, 2006
Am trying to build a simply irrigation controller with 25 zones.
Each zone would be sequenced on for about 15 minutes at a time until
all 25 zones were activated. I am controlling each zone with a
Rayex LU-5 PC mount relay, that has a coil voltage/ohms of 5VDC/125
ohms.

What is the most reliable way of controlling these 25 relays with
the BX-24?

I've already tried, a bit quickly, using row-column array that
didn't work very well. I believe that more than one relay was
getting voltage at a time, causing the desired relay not to
energize. Could explain in more detail if anyone wanted.

However at this point, I'm more interested in what people think is
the best METHOD of controlling multiple outputs.

Is it the above row-column array, or shift register, or latch, or
multiplexer, or something else? Don't want to spend an extravagant
amount of money, but would spend some on a good reliable method.

Does anyone have any experience with something like this?

Thank you

Abe Fanning
Since your update rate is immaterial, I'd use a shift register.

If you can work with SMDs, the MAX4820 is a single-part, 8-channel
solution, so four cascaded parts will drive your 25 (or 32) 5v relays
directly, controlled via SPI.

If you want to build something similar, four 74HC164s
(serial-to-parallel shift registers) and four ULN2803s (current drivers)
should work well.
Tom
Abe
This is a very simple application. Use 4 x UCN5821 serial to
parallel driver chips ( there are others). You will need a simple peice
of code to send the data and clock pulses to the UCNs and you only need
3 lines of the BX24. The UCN will drive your relays directly. In the
files section, I have a small article on how to drive the UCN including
code.
neil

abefanning wrote:

> Am trying to build a simply irrigation controller with 25 zones.
> Each zone would be sequenced on for about 15 minutes at a time until
> all 25 zones were activated. I am controlling each zone with a
> Rayex LU-5 PC mount relay, that has a coil voltage/ohms of 5VDC/125
> ohms.
>
> What is the most reliable way of controlling these 25 relays with
> the BX-24?
>
> I've already tried, a bit quickly, using row-column array that
> didn't work very well. I believe that more than one relay was
> getting voltage at a time, causing the desired relay not to
> energize. Could explain in more detail if anyone wanted.
>
> However at this point, I'm more interested in what people think is
> the best METHOD of controlling multiple outputs.
>
> Is it the above row-column array, or shift register, or latch, or
> multiplexer, or something else? Don't want to spend an extravagant
> amount of money, but would spend some on a good reliable method.
>
> Does anyone have any experience with something like this?
>
> Thank you
>
> Abe Fanning
>
>
>
>
>
>
So I also do a similar project.
I use the electric valves from old washing machines and these are
controlled by cheap solid-state relays directly driven by the
74ls164's. There are 6 in a row giving me 6 x 8 = 48 bits.
This is using 3 I/O pins on my BX24. ( Data, Clock, Output-Enable)
Some of the bits are used to drive leds and displays the others the
relays.

Wim

--- In b..., "abefanning" wrote:
>
> Am trying to build a simply irrigation controller with 25 zones.
> Each zone would be sequenced on for about 15 minutes at a time
until
> all 25 zones were activated. I am controlling each zone with a
> Rayex LU-5 PC mount relay, that has a coil voltage/ohms of 5VDC/125
> ohms.
>
> What is the most reliable way of controlling these 25 relays with
> the BX-24?
>
> I've already tried, a bit quickly, using row-column array that
> didn't work very well. I believe that more than one relay was
> getting voltage at a time, causing the desired relay not to
> energize. Could explain in more detail if anyone wanted.
>
> However at this point, I'm more interested in what people think is
> the best METHOD of controlling multiple outputs.
>
> Is it the above row-column array, or shift register, or latch, or
> multiplexer, or something else? Don't want to spend an extravagant
> amount of money, but would spend some on a good reliable method.
>
> Does anyone have any experience with something like this?
>
> Thank you
>
> Abe Fanning
>
Yes, right, I use the 74LS164 for driving a bunch of 7-segment
displays. So saving a lot of I/O pins on my BS24.
There is a nice command SHIFTOUT to drive the shiftregisters.
Just 2 pins.

Wim
--- In b..., "njepsen@..." wrote:
>
> Abe
> This is a very simple application. Use 4 x UCN5821
serial to
> parallel driver chips ( there are others). You will need a simple
peice
> of code to send the data and clock pulses to the UCNs and you only
need
> 3 lines of the BX24. The UCN will drive your relays directly. In
the
> files section, I have a small article on how to drive the UCN
including
> code.
> neil
>
> abefanning wrote:
>
> > Am trying to build a simply irrigation controller with 25 zones.
> > Each zone would be sequenced on for about 15 minutes at a time
until
> > all 25 zones were activated. I am controlling each zone with a
> > Rayex LU-5 PC mount relay, that has a coil voltage/ohms of
5VDC/125
> > ohms.
> >
> > What is the most reliable way of controlling these 25 relays with
> > the BX-24?
> >
> > I've already tried, a bit quickly, using row-column array that
> > didn't work very well. I believe that more than one relay was
> > getting voltage at a time, causing the desired relay not to
> > energize. Could explain in more detail if anyone wanted.
> >
> > However at this point, I'm more interested in what people think is
> > the best METHOD of controlling multiple outputs.
> >
> > Is it the above row-column array, or shift register, or latch, or
> > multiplexer, or something else? Don't want to spend an extravagant
> > amount of money, but would spend some on a good reliable method.
> >
> > Does anyone have any experience with something like this?
> >
> > Thank you
> >
> > Abe Fanning
> >
> >
> >
> >-------------------------------
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> >
> >No virus found in this incoming message.
> >Checked by AVG Free Edition.
> >Version: 7.1.405 / Virus Database: 268.12.3/446 - Release Date:
12/09/2006
> >
>
Neil,

Thank you very much for responding. It seems that a shift
register/latch is the way to go in my case. I like the idea of
cascading chips using the serial out pin.

I've looked for the UCN5821 you mentioned and can't seem to find
any. I think they are discontinued. The closest I could fine is a
Micrel MIC5821BN-ND at Digikey. The data sheet looks like the exact
same thing as the UCN5821.

Could you suggest a place to purchase either/same?

Thank you
Abe Fanning

njepsen wrote:
>
> Abe
> This is a very simple application. Use 4 x UCN5821
serial to parallel driver chips (there are others).[]
wimn,

Thank you very much for responding. I like the idea of a shift
register/latch for my project.

Do you use the 74LS164 in a cascading scheme, i.e. connect them end
to end using a serial out pin so you can have multiples of 8 output
pins? The datasheet for the 74LS164 does not have a serial out pin
to connect to the next chip. Is there another way, or am I missing
something?

Thank you
Abe Fanning

--- In b..., "wimn.rm" wrote:
>
> Yes, right, I use the 74LS164...[]
> ... the 74LS164 does not have a serial out pin...

Look again at the logic diagram. Q7 is the last of eight shift
register outputs; connect it to one of the next package inputs and
clock it.

http://www.fairchildsemi.com/ds/74%2F74VHC164.pdf#search=%2274hc164%22
Tom
Preferr the 74hc595 over the 74ls164. It has a built-in latch so your
outputs don't see the new values ripple by. Sometimes that can be an
issue.

And as someone else mentioned earlier, you can use a ULN2803 as a
driver on the output of the register/latch.

--- In b..., "abefanning" wrote:
>
> wimn,
>
> Thank you very much for responding. I like the idea of a shift
> register/latch for my project.
>
> Do you use the 74LS164 in a cascading scheme, i.e. connect them end
> to end using a serial out pin so you can have multiples of 8 output
> pins? The datasheet for the 74LS164 does not have a serial out pin
> to connect to the next chip. Is there another way, or am I missing
> something?
>
> Thank you
> Abe Fanning
>
> --- In b..., "wimn.rm" wrote:
> >
> > Yes, right, I use the 74LS164...[]
>
"wimn.rm" wrote:

> ... I use the electric valves from old washing machines...

FYI, Orbit sells an inexpensive 12vDC _latching_ water control valve.
http://www.orbitonline.com/products/product.cfm?id022&subcat$11
Tom